Gypsum stucco



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Patented July 23, 1955 UNITED STATES Q N Examiner PATENT OFFICE GYPSUM s'ruooo No Drawing. Application July 11, 1934, Serial No. 734,704

'1 Claims.

This invention relates to an improved stucco, preferably. made from gypsum, and the method of making the same, the prime use of which is the manufacture of lightweight plaster board therefrom. It is also elfective for the manufacture of light weight tile and other similar uses as will hereinafter more clearly appear. The plaster board made from this improved stucco has characteristics which give it unusual strength and this board is also much lighter in weight as compared to the plaster boards now in use.

For a number of years plaster board manufacturers have endeavored to produce a board which is light in weight in order to reduce the high freight and hauling expense of its transportation as well as the labor cost of handling the heavy board.

Many processes have been applied in producing a light weight plaster board with more or less varying results. In most cases elaborate machinery and equipment has had to be installed to prepare or process admixtures such as soap bubbles, gas or other void-producing agents, which, by means of other elaborate devices, are mixed with the stucco during the process of manufacture of plaster board.

As a rule, one thousand square feet of'plaster board as now in the present market weigh from 1,800 to 2,000 pounds the thickness of said board being exactly five eighths of an inch. An enormous saving can be obtained through the use of my invention as by it the weight of the board may be reduced to say 1,500 pounds a thousand square feet and the resulting light weight board is as strong as the heavier board and its quality fully conforms to the required standard building specifications.

With my invention I produce a light weight plaster board which not only saves freight and labor costs as indicated but I also eliminate the special and elaborate equipmentnow used to produce a light weight plasterboard-after the calcined stucco leaves the calcining kettles.

As this invention is of the material itself and the preferred method of making the material, it is not believed necessary to explain the details of forming boards, tiles or the like therefrom.

I simply mix in any appropriate manner a small percentage of a certain inexpensive material with the stucco material, said stucco material preferably being raw gypsum (calcium sul hate) and preferably Beiore the raw gypsum enters the calciners, said materials being fed automatically, if desired, by self-dumping, self-weighing scales.

It is a well known phenomenon that raw vermiculite when subjected to a moderate hea will expan up to twenty per cent in size of its bulk. This phenomenon also occurs even though the raw vermiculite has been reduced to very small sizes (almost powder) said small sized almost powdered vermiculite being referred to herein as comminuted vermiculite which I have discovered to be peculiarly effective in making plasterboard cores and to distinguish it from the coarser (granulated not comminuted) vermiculite which I am aware may be used in other products.

I have discovered that by decreasing the size of the particles of vermiculite a product of improved structure and strength peculiarly adapt- 5 ed to the making of plasterboard cores may be made therefrom, When these particles are comminuted particles they may be included in sufficient number and with such distribution to produce a board of unique and improved texture 20 with special characteristics said board being unusually strong as well as light in weight. Should the particles of vermiculite be as large as the particles used in some products the characteristics of the final mass will be different and the 25 particles will also be unduly large in proportion to the thickness of the core of the plaster board which is not desirable.

When such expanded vermiculite is examined under the microscope it will be found to contain 30 uncountable voids or air cells. A cubic foot of spghmxnandedamaterialawetghs fnly hq gm six L/"' sum stucco. A pubic foot of st -1 l 40 proximately sixty-five pounds. The bulk of the stmthan the expanded vermiculite and it can be readily seen that the presence of only 6% to 10% of the vermiculite, preferably expanded and included as herein shown, will increase the bulk of the stucco considerably, or, in other words, the weight of the mixture for a given cubic content will be considerably less.

I have found that the admixture of approximately ten percent of raw comminuted vermiculite to one ton of ulverized raw gypsum stucco will, when calcined in appropriate equipment for the making of plaster board'core, produce a board that is very strong and which is stable in every respect. This also reduces the weight of a thousand square feet of board five-eighths of an inch thick to the extent of five hundred (500) pounds. I. have found that when the vermiculite is comminuted (reduced almost to a powder) the unit particles being smaller than the vermiculite particles used in other products this imparts to the mass a texture of such character that the final mass when dried out is light in weight and very strong which is highly satisfactory.

The preferred process as herein described has special advantages as will hereinafter more fully appear. However, a plasterboard which contains expandedpomminuted vermiculite as discovered by me wilfobviofisly' have unusual merit irrespective of the method by which the core which contains the comminuted vermiculite is fabricated.

Calcined stucco as bought in the open market contains at times as high as five per cent and more of uncalcined gypsum due to the improper or too hasty calcination thereof. This condition is also eliminated by my invention when the raw vermiculite is mixed with and heated with the raw stucco and is intimately mixed with the stucco, as it swells while it is in this intimate mixture which gives the heat an opportunity to more readily reach all the particles of gypsum resulting in thorough calcination which greatly improves the stucco.

When the making of relatively thick products or tiles is contemplated from a plaster mix made by this preferred process of heating together raw vermiculite and raw ypsum rather than relatively thin plasterboard the particles of raw vermiculite included with the raw gypsum may be somewhat larger.

In giving this detailed description of my invention I wish it to be understood that it is illustrative and that my invention is not limited to particular proportions of ingredients and application except in accordance with the spirit and scope of the appended claims.

Having described my invention, I claim:

1. A plaster mix ready to be calcined consisting of pulverized raw gypsum and raw vermiculite, said raw vermiculite being included in sufficient amount to reduce the weight per unit volume of the mass by from 15% to 25% after said plaster mix has been calcined.

2. A plaster mix ready to be calcined said mix consisting of pulverized raw calcium sulphate and comminuted raw vermiculite.

3. The method of making a stucco mix which when wetted with water will set into a hard mass which comprises mixing together pulverized raw gypsum stucco approximately 90% to 94% by weight and raw vermiculite approximately 6% to 10% by weight and thereafter calcining the mixture in appropriate calcining equipment.

4. A plaster mix ready to be calcined said mix consisting of pulverized raw gypsum and granulated raw vermiculite.

5. The method of making an improved stucco which consists of calcining a mixture of pulverized raw gypsum and granulated raw vermiculite.

6. The method of making an improved stucco which consists of calcining a mixture of pulverized raw gypsum and comminuted raw vermiculite.

'7. A process which includes the steps of calcining a body of gypsum and heating a body of raw vermiculite, the heating of said vermiculite being concurrent with at least a portion of said calcining step and carried out while said bodies are intimately admixed.

GUSTAVE ADOLPH NEW. 

